This invention relates generally to improved dwell and depth attachments for power drills and the like. More particularly, but not by way of limitation, this invention relates to an improved dwell and depth attachment for power drills and the like that includes means for precisely setting the depth to be drilled.
A number of attempts have been made in the past to accurately control the depth of a drilled hole as measured from the surface of the material in which the hole is drilled. While it can be accomplished manually by carefully drilling each hole, it becomes a more difficult problem when high accuracy and repeatability are to be accomplished in relatively high production situations. Attempts to provide apparatus for controlling the depth are illustrated by U.S. Pat. No. 3,767,313 issued Oct. 23, 1973 to Luis A. Bohoroquez et al and U.S. Pat. No. 4,273,481 issued June 16, 1981 to John E. Corley et al.
A relatively successful variable dwell control attachment with depth control was invented by Harold R. Ziegelmeyer and described in U.S. Pat. No. 3,762,827 which issued on Oct. 2, 1973. In this device, a sensing sleeve encircles the spindle that drives the drill bit, and the drill bit is capable of telescoping through the sensing sleeve. The spindle driving the drill bit carries on its lower end, an adjustable stop sleeve. The stop sleeve is engageable with the upper end of the sensing sleeve to limit the travel of the spindle and the drill bit. Adjustment of the drilling depth is obtained by positioning the stop sleeve that is threaded on the spindle, by simple rotation of the sleeve relative to the spindle. This device is very simple and generally accurate. It is difficult to obtain precise adjustment since there is no positive means for knowing how far the stop sleeve is rotated relative to the spindle.
An object of this invention is to provide an improved dwell and depth attachment for power drills or the like that can be adjusted to provide precise settings for drilling depth.